Significance of soil saturation on stability of a high sandy embankment
Gallage, Darshana (2026)
2026
Master's Programme in Civil Engineering
Rakennetun ympäristön tiedekunta - Faculty of Built Environment
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Hyväksymispäivämäärä
2026-06-30
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202606298031
https://urn.fi/URN:NBN:fi:tuni-202606298031
Tiivistelmä
Stability of embankments is strongly affected by their hydro-mechanical behaviour. The influence of partial saturation is often ignored in conventional stability analyses. This thesis investigates the significance of soil saturation on stability of a sand embankment section which collapsed twice in recent history. The main research question addressed is how changes in the degree of saturation influence embankment stability.
A brief description of failures and possible failure mechanism is presented. Literature review consists of fundamentals of unsaturated soil mechanics and Barcelona Basic Model (BBM). BBM was used to model the unsaturated behaviour in Plaxis 2D. In addition to basic laboratory tests, laboratory testing program included the determination of the Soil Water Retention Curve (SWRC), series of triaxial compression tests performed under different water contents. The experimental results were used to evaluate changes in shear strength with degree of saturation. Tri-axial tests results did not indicate clear trend of shear strength with different water content levels. However, based on the triaxial test results, key parameters of the BBM were calibrated and model was able to predict reasonable shear strength values compared to experimental. The calibrated material model was implemented in Plaxis 2D to assess embankment stability under different saturation levels. Baselines calculations were conducted without considering suction to quantify effects of suction. The results indicated that the suction increase the factor of safety by 12% at most at a degree of saturation of 0.2.
A brief description of failures and possible failure mechanism is presented. Literature review consists of fundamentals of unsaturated soil mechanics and Barcelona Basic Model (BBM). BBM was used to model the unsaturated behaviour in Plaxis 2D. In addition to basic laboratory tests, laboratory testing program included the determination of the Soil Water Retention Curve (SWRC), series of triaxial compression tests performed under different water contents. The experimental results were used to evaluate changes in shear strength with degree of saturation. Tri-axial tests results did not indicate clear trend of shear strength with different water content levels. However, based on the triaxial test results, key parameters of the BBM were calibrated and model was able to predict reasonable shear strength values compared to experimental. The calibrated material model was implemented in Plaxis 2D to assess embankment stability under different saturation levels. Baselines calculations were conducted without considering suction to quantify effects of suction. The results indicated that the suction increase the factor of safety by 12% at most at a degree of saturation of 0.2.